of a Wing
Wings has soft, smaller feathers towards the top of the wing and longer feathers towards the edges, particularly the tip. Note the difference when the wing is extended versus folded and how the feathers are placed.
to the right is how wings work when folded and extended.
There are three bones with two joints. The third joint is
connected to the back of torso. If you need something to
physically look at, check out a chicken wing next time you
come across one... :)
Feathers are fairly easy to draw. The ends can vary from thin to wide. Ending at a point like a double-edged sword or a single-edged katana. There are three types of feathers. The long, the medium, and the smallest with the fluffy top (aka "down" feather).
Going back to bat wings, what's shown on the left is the basic general construct. The bones acts as a wire frame with the leathery skin over it creating a webbing that works as well as feathers. The bottom of the web are like drawing hills. How flat or "hilly" it is depends on how the wing is - extended or folded. An extended wing creates a more "flattened" hill than a folded wing.
Also notice the pointy bone at the top of the joint. This is usually just a bone poking out of the skin. At times, this is illustrated as a claw or hand-like bone shown in the middle. Make sure you add the detail of the skin wrapping around the bone!